linux-kernel - Re: [PATCH] MAINTAINERS, x86/CPU: Tony Luck will maintain asm/intel-family.h

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Message-ID: <20190815175455.GJ15313@zn.tnic>
Date:   Thu, 15 Aug 2019 19:54:55 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     "Luck, Tony" <tony.luck@...el.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Dave Hansen <dave.hansen@...el.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] MAINTAINERS, x86/CPU: Tony Luck will maintain
 asm/intel-family.h

On Thu, Aug 15, 2019 at 10:21:59AM -0700, Luck, Tony wrote:
> Like this?

Actually, I was thinking you'd put it above the defines in the file
intel-family.h itself so that *everyone* who wants to add a model, sees
it first and while that explanation below is very nice...

> +The CPU model number on a running system can be found by executing
> +the CPUID(EAX=0) instruction to find the vendor, family, model
> +and stepping.  The model number is found by concatenating two bit
> +fields from the EAX return value. Bits 19:16 (extended model number)
> +and 7:4 (model number).
> +
> +Inside the Linux kernel the vendor, family, model and stepping are
> +stored in the cpuinfo_x86 structure. Model specific code typically
> +uses x86_match_cpu() to determine if it is running on any of some
> +list of CPU models.
> +
> +There are several subsystems that need model specific handling on
> +Intel CPUs. For code legibility it is better to assign names for
> +the various model numbers in the include file <asm/intel-family.h>
> +
> +Currently all interesting Intel CPU models are in family 6.

.. we're probably going to need the text only from here on down:

> +
> +HOWTO Build an INTEL_FAM6_ definition:
> +
> +1. Start with INTEL_FAM6_
> +2. If not Core-family, add a note about it, like "ATOM".  There are only
> +   two options for this (Xeon Phi and Atom).  It is exceedingly unlikely
> +   that you are adding a cpu which needs a new option here.
> +3. Add the processor microarchitecture, not the platform name
> +4. Add a short differentiator if necessary.  Add an _X to differentiate
> +   Server from Client.
> +5. Add an optional comment with the platform name(s)
> +
> +It should end up looking like this:
> +
> +INTEL_FAM6_<ATOM?>_<MICROARCH>_<SHORT...> /* Platform Name */
> -- 

Thx.

-- 
Regards/Gruss,
    Boris.

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